500 times. This suggests those vegetation types were 

 25 times as resistant to trampHng damage. 



After the year of recovery, cover loss still varied 

 among vegetation tjrpes, but the number of types dif- 

 fering from each other declined. In one region, only 

 one type differed from one other type. In two regions, 

 one type was different from the other three; in the 

 other region, two types were different from the other 

 two. Although the response of most vegetation types 

 became more similar over the year of recovery, this was 

 not the case for aU t5T)es. The magnitude of difference 

 between the most and least durable types, 1 year after 

 trampling, was about the same as it was immediately 

 after trampling. The most tolerant type, Trifolium, 

 had relative cover of 96 percent 1 year after 500 passes, 

 while the least tolerant type, Vaccinium, had just 14 

 percent relative cover. One year after trampling, paths 

 could not be seen on the most heavily trampled lanes 

 in nine vegetation types, while in Phyllodoce and Vac- 

 cinium paths were evident on 200-pass lanes. 



These results suggest that if most trampling can be 

 confined to more resistant vegetation types, impacts 

 can be reduced dramatically. Some of the more resis- 

 tant types can handle 25 to 30 times as much use as 

 less resistant types. Most vegetation types lost most 

 of their cover after 100 to 200 passes; however, a few 

 types retained most of their cover even after 500 passes. 

 Six of the vegetation types had largely recovered, 1 year 

 after trampling, even on the lanes that received 500 

 passes. However, in several types, lanes trampled 

 only 200 times remained largely devegetated 1 year 

 later. Most vegetation types recovered from several 

 hundred passes, but not from 500 passes. These fig- 

 ures should provide some estimates of the use levels 

 Ukely to lead to traU formation in areas without trails. 



Effects of Various Levels of Trampling 



In most of these vegetation types, fewer than 100 

 people following the same route will leave an evident 

 path that is Likely to attract others. On the other hand, 

 several types are so durable that a few himdred people 

 following the same route will leave virtually no evi- 

 dence of their passing. 



In attempting to assess acceptable levels of tram- 

 pling, a number of impact indicators might be used. 

 Two seem particularly useful, given the objective of 

 maintaining an area in a trailless condition: (1) the 

 level of trampling that leaves an evident path (be- 

 cause an evident path encourages additional use) 

 and (2) the level of trampling with impacts that do 

 not disappear within 1 year (levels likely to cause 

 long-term impact). Data suggest that, to keep trails 

 from developing, no more than about 75 people should 

 follow the same route through Phyllodoce, Vaccinium, 

 and Lycopodium. Similar maximum levels would be 

 about 100 to 150 people in Pachistima, Leersia, Carex 



pensylvanica, Amphicarpa, and Dryopteris. Maximvun 

 use levels would be several hundred people in Valer- 

 iana, Geranium, Carex bigelowii, Maianthemum, and 

 Potentilla. Carex nigricans, Kobresia, and Trifolium 

 probably could tolerate about 400 people following 

 the same route in 1 year. 



These data could be interpreted differently. Data 

 presented for each vegetation type should help manag- 

 ers assess the likely impacts associated with various 

 levels of use. Data can be extrapolated, with caution, 

 to other vegetation types with similar growth forms. 



Factors That Influence Response 



These data improve our abihty to predict the dura- 

 bility of different vegetation types. Several hypotheses 

 about the durabiUty of vegetation have been advanced. 

 Some suggest regional differences, such as between 

 the Eastern and Western United States (Hall 1989). 

 Others suggest differences related to environmental 

 gradients (Kuss 1986). Finally, others have tended 

 to explain variation on the basis of vegetation charac- 

 teristics (Kuss 1986; Liddle 1991). 



The importance of these factors was assessed by 

 examining their influence on cover loss and recovery 

 following trampling. Figure 37 depicts the resistance, 

 resilience, and tolerance of the 16 vegetation types in 

 the four regions. There were pronounced differences, 

 among vegetation types, in each of these three attri- 

 butes. Carex nigricans was most resistant. Dryopteris 



Relative Cover After Trampling (percent) 

 Resistance Index 



Figure 37 — Resistance, tolerance, and re- 

 silience of the 1 6 vegetation types in all 

 four regions. Resilience is indicated by the 

 perpendicular distance from the diagonal 

 line of equal resistance and tolerance. 



48 



